The present invention relates to the application of a treating medium to a workpiece.
More particularly, the invention relates to the application of a foamed treating medium to a workpiece.
Still more particularly, the invention relates to the application of a foamed treating medium to a sheet-material workpiece, especially a textile workpiece.
Yet more specifically, the invention relates to an applicator for applying the foamed treating medium to such a workpiece.
Foaming of a treating medium, and its application to a workpiece, are known from German Pat. No. 2,523,062. In that patent the foamed treating medium is admitted into the top of a box-shaped receptacle whose cross-section diverges sharply in direction away from the relatively small foam inlet of the receptacle. Baffles in the interior of the receptacle are to assure improved distribution of the foam.
This construction makes no provision for keeping the upper level of the admitted foam uniform--nor is there any need to do so since the distance between the foam inlet and foam outlet regions is relatively large, the cross-section of the box interior diverges in direction towards the foam outlet, and the foam volume is limited in the upward direction by the use of a box as the receptacle.
A problem is encountered, however, when relatively wide sheet- or band-material workpieces, especially textile workpieces, are to be printed, colored, coated or otherwise treated with foamed treating medium. To obtain high-quality results it is a requirement that there be assurance that the treating medium will penetrate into the substrate (i.e. the workpiece) to a depth which is uniform over the entire length and width of the workpiece as well as for the entire time-period of the production run. Hand in hand with this goes the further requirement to maintain completely uniform foam application conditions over long production periods, for example in the case of large production runs.
When the foamed treating medium is to be applied to a relatively wide workpiece, then evidently the chamber from which the medium is discharged onto or towards the workpiece must be of commensurate width. Admission of the treating medium into this chamber is simply a matter of discharging it into the chamber from a supply tube which is similar to the ink-supply tube used in a screen-printing machine but must, of course, have substantially larger outlet openings. Since all such foam, whether it is completely stable or slightly unstable, essentially refuses to flow, it is self-evident that underneath the tube outlet openings the foamed treating medium will form peaks--and that at these peaks the depth of foamed treating medium in the chamber will be greater than elsewhere. Accordingly, the prior art does not fulfill the above-mentioned essential requirement, namely that completely uniform foam application conditions be maintained for long production run periods over the entire width of the workpiece area to which the treating medium is being applied.